Double acting apparatus and method for ejecting workpieces from forming machines

ABSTRACT

A resilient element is used to eject a workpiece from a machine, such as a lidded container from a seaming chuck. The resilient element dual acting since it is formed of a flexible compressible material in a manner so that a first portion of the element applies a first ejecting force and a different, second portion applies a second ejecting force after completion of a task on the workpiece. This can be by a combination of flexion and compression. The resilient element can have a central panel portion of flexible resilient material and a margin portion of compressible material. A head can be formed on the central panel portion. The invention includes a chuck assembly provided with such resilient element. The invention also includes a method of ejecting workpieces from machines with the dual restorative forces.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/245,787, filed Nov. 3, 2000.

FIELD OF THE INVENTION

[0002] The present invention broadly concerns metal forming machinesand, particularly, ejector apparatus and methods for ejecting aworkpiece from the metal forming machine. More specifically, however,the present invention is directed to the ejector apparatus for use withlid seamers for ejecting lidded containers such as those made with afiberboard, metal or plastic side wall and a metal lid seamed on a toprim thereof.

BACKGROUND OF THE INVENTION

[0003] The use of automated machinery to perform machining functions onworkpiece has become an essential part of modern manufacturingtechnology. In such automated equipment, it is typical that one or moreforming stations are provided. A workpiece is advanced into engagementwith the forming station by means of a positioning mechanism. Uponretraction of the positioning mechanism, the workpiece is ejected fromthe forming station so that the metal forming cycle can be repeated.Ejection of the formed workpiece is accomplished by gravity or, in someinstance, by an ejector rod that may, for example, be mechanicallyactuated to apply a jarring force to the workpiece to eject theworkpiece from the forming station.

[0004] A specific example of such a machine adapted to perform amachining function, and the type of machine to which the presentinvention is particularly directed, is a lid seamer. Such seamers aretypically of a type used for concentrated juices, meat products, oilcontainers and the like. Here, the container has a plastic, metal orfiberboard sidewall affixed to a bottom end. The bottom end is seamed tothe lower sidewall rim before filling. The sidewall has an upper rimthat defines a mouth so that the container may be filled with product.After filling, a lid is registered with the upper rim so that thecombination lid and rim are seated on a chuck assembly as a workpiece.One or more forming rollers then revolve around the chuck element toseam the lid onto the container to produce a sealed, lidded containerthat is then ejected for further packaging, as desired. The workpiece isgenerally moved into position through the use of a star-wheel apparatus.In some instances, a threaded pull strip is provided around the rim andis seamed at the lid/sidewall interface concurrently with the lid toprovide a structure for ease of opening the finished container. Thestandard ejector mechanism is in the form of a knock-out rod which iscam-actuated so as to be mechanically timed to tap the center of thelidded container thereby to eject it from the chuck assembly in theforming station.

[0005] Use of knock-out rods of a type typically employed in theindustry is not without its problems, however. Where the sidewall of thecontainer is constructed of fiberboard or plastic, a greater knock-outforce is employed due to increased friction between the containersidewall and the star wheel apparatus. Lids for these containers caneven have an undercut (about 3°to 7°) which may aid the release of thelidded container from the chuck after seaming. Even where only a slightforce is necessary to eject a lidded container, the impact of theknock-out rod on the center of the formed container can damage the lidcausing scratching, denting, contamination, loss or degradation of theproduct.

[0006] Several other disadvantages arise from the use of a knock-outrod. One such disadvantage is the fact that the knock-out rod along withits associated mechanical structure, including cam followers, camgrooves and the like, greatly increase the complexity of most lidseamers. Thus, such machines are expensive and costly to maintain.Moreover, since the knock-out rod reciprocates in an assembly mounted onthe center of the forming chuck, it is necessary to lubricate theknock-out rod and its associate bushings, bearings, etc. The presence oflubricants always presents the problems of leakage that, in rareinstances, might contaminate the product in the container or soil thecontainer lid. Further, the inertial mass of the reciprocating knock-outrod and its associated mechanical linkages acts as a limit on the speedat which such machines can operate.

[0007] In my U.S. Pat. No. 5,533,853 issued Jul. 9, 1996, 1 disclose animproved ejector apparatus and method for machines in general andespecially lid seamers, which utilizes a resilient element mounted on achuck. The resilient element is positioned so that, when the workpieceis in an engaged position, a portion of the workpiece engages theresilient element to collapse the resilient element. When thepositioning mechanism retracts, the resilient element exerts arestorative force on the workpiece thereby to eject the workpiece fromthe forming station. In this patent, it is preferred that the resilientelement be polymer-based.

[0008] Where containers are made of fiberboard or plastic, or in someinstances metal, a greater amount of work (as defined by force actingover distance) may be necessary due to the dimensions of the lid, theabove noted undercut and other geometry of the machinery. I have learnedthat, when ejecting such a container from a lid seamer, it is desirableto have a stronger force acting over a relatively small distance toinitially eject the container from the chuck but to also have a lesserforce acting over a longer distance to completely insure dislodgment ofthe lidded container after the seaming operation and before gravity canbe effectively implemented to discharge the container. Thus, despite theadvances described in the above-named patent, there is a need forimproved ejector apparatuses, especially as applied to ejectorapparatuses, machines using ejectors, particularly lid seamers, used inthe production of fiberboard, plastic or other containers. The presentinvention is directed to meeting these needs.

SUMMARY OF THE INVENTION

[0009] It is an object of the present invention to provide a new anduseful improvement to machines that require ejector mechanisms thatassist in ejecting a workpiece from a forming station.

[0010] Another object of the present invention is to provide an ejectorapparatus that reduces the complexity of the forming machinery.

[0011] A further object of the present invention is to provide apparatusand a method employing a double acting resilient ejector for use inejecting workpieces from forming stations.

[0012] Another object of the present invention is to provide an ejectorapparatus and method for lid seamers which reduces the incidence ofcontamination by lubricating media.

[0013] Yet another object of the present invention is to provide a newand useful chuck assembly incorporating an ejector apparatus that mayretrofit onto existing machines, especially lid seamers, that reducesthe cost of maintaining such machinery.

[0014] Still another object of the present invention is to provide a newand useful ejector apparatus especially suited for use with formingmachines used for the formation of fiberboard, metal or plastic sidewall containers with seamed tops and bottoms, such as metal end caps.

[0015] A further object of the present invention is to provide animproved method and improved ejector apparatus which may allow automatedmachining functions to proceed at greater speeds.

[0016] Yet another object of the present invention is to eliminatetraditional knock-out rods and associated parts from lid seamers thusreducing the parts count of the seamers.

[0017] According to the present invention, then, a resilient element isprovided for a chuck assembly with this chuck assembly being adapted tomount in a machine that performs a machining function on a workpiece.Such machine has at least one forming station including at least oneforming roller and at least one chuck element having a forming surfacecooperative with the forming roller to perform the machining function.The machine also has a positioning mechanism operative to advance so asto move the work piece from a disengaged position through anintermediate position and into an engaged position so that the machiningfunction can be preformed. The positioning mechanism retracts so thatthe workpiece can be ejected from the forming station. An example ofsuch a machine is a lid seamer or other machine to place an end closureon a container body, such as used in the food and beverage industry.

[0018] The resilient element then forms an improvement to this chuckassembly, and thus, such machines. The resilient element is formed of aflexible, compressible first material and is mounted to the chuckelement and positioned so that, when the workpiece is in theintermediate position, a first portion of the resilient element isoperative to apply a first force to the workpiece. When the workpiece isin the engaged position, a second portion of the resilient element thatis different from the first portion is operative to supply a secondforce to the workpiece. Thus, as the positioning mechanism retracts, thefirst and second portions of the resilient element exert first andsecond restorative forces, respectively, on the workpiece thereby toeject the workpiece from the forming station.

[0019] The first portion of the resilient element is defined by acentral region, and the second portion is defined by a marginal region.The marginal region is formed as a peripheral lip extending around theperimeter of the resilient element and has a thickness that is greaterthan the thickness of the central region. A head structure is providedon the central region. This head structure may be an integral one-piececonstruction with central region. For example, the head structure caninclude a rounded contact surface to contact the workpiece when it ismoved from the disengaged position toward the intermediate position.Alternatively, the head structure has a flat contact surface to contactthe workpiece when it is moved from the disengaged position toward theintermediate position. In one embodiment, the head structure is definedby a plug disposed on the central region. This plug has an enlargedhead, in the form of a button, that is supported on an elongated, axialshaft. This axial shaft extends through a hole in the central portionand may be retained thereon by means of a locking washer engaging vaneson the shaft of the plug. Here, the plug is formed of the secondmaterial different than the material used to construct the resilientelement, and this material may be labrusish material, such as nylon. Inaddition, the central region may be prorated with a stanchion, such asan annular ring formed integrally with the central region, so thisstanching ring may support the button portion of the plug.

[0020] The resilient element, along with the chuck element of thepresent invention thus forms a chuck assembly. The chuck element then ismountable to the machine. The chuck element has a rim that provides aforming surface that cooperates with the forming roller to perform themachining function and a recess is bounded by this rim. The resilientelement is then mounted to the chuck element and disposed in the recess.To accomplish this, the chuck element may have a groove formed in therecess proximately to the rim such as the groove is bounded by the rimin an inner groove wall. One wall of the groove can be formed a largeacute angle relative to a transverse plane that is orientatedperpendicularly to the central axis of the chuck assembly. The resilientelement then includes a ridge structure that projects away from a firstside thereof. The ridge structure can be formed in a large acute angleso that the ridge structure and the groove may be snap fitted together.This ridge structure is thus operative to be matably received in thegroove thereby to secure the resilient element in a fastened state tothe chuck element with the marginal region supported against an exposedsurface to the inner groove wall.

[0021] The chuck assembly can have an axial passageway extendingtherethrough in communicating with the recess. When mounted, the centralpanel region of the resilient element extends transversely across thisaxial passageway with a marginal region being formed as a peripheral lipextending around the perimeter of the resilient element. The centralregion of the resilient element then has at least one vent port formedtherethrough and can include a plurality of vent ports formedequiangularly around the axis.

[0022] The present invention also then is directed to a method ofejecting a workpiece from a machine of the type described above. Thismethod includes the steps that are inherent in the above describedstructure. Broadly, the method includes a step of securing a resilientelement in fixed relation relative to the chuck element in the machinein a manner such that a central portion of the resilient element will becontacted by and deflected by the workpiece when the workpiece is movedinto the intermediate position thereby to exert a first restorativeforce tending to eject the workpiece from the chuck element. The methodthen includes advancing the positioning mechanism so that the workpiecemoved from the intermediate position into the engaged positionsimultaneously compressing a margin portion of the resilient elementthereby to exert a second restorative force tending to eject theworkpiece from the chuck element. The method then includes the step ofholding the workpiece in the engaged position against the restorativeforces until the machining function is completed and thereafterretracting the positioning mechanism to allow the resilient element torebound to eject the workpiece. The resilient element is constructed sothe first and second restorative forces applied thereby are sufficientto eject the workpiece from the forming station after the machiningfunction is preformed thereon. In this method, the machine may be a lidseamer wherein the machining function is seaming an end closure onto acontainer body.

[0023] These and other objects of the present invention will become morereadily appreciated and understood from a consideration of the followingdetailed description of the exemplary embodiments of the presentinvention when taken together with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 is a perspective view in partial cross-section showing alid seamer according to the prior art for seaming a lid onto afiberboard, metal or plastic container;

[0025]FIG. 2 is a perspective view of a chuck element with which thepresent invention may be used;

[0026]FIG. 3 is an exploded view in partial cross-section of the chuckassembly shown in FIG. 2 along with a resilient element to be mountedthereon;

[0027]FIG. 4 is an exploded perspective view of the first exemplaryembodiment of the resilient element according to the present invention;

[0028]FIG. 5 is a side view in cross-section showing the mounting of oneedge of the resilient element and the chuck element of the firstexemplary embodiment of the present invention;

[0029]FIG. 6(a) is a side view in partial cross-section showing acontainer engaging the chuck element of the first exemplary embodimentof the present invention in a fully engaged position;

[0030]FIG. 6(b) is a side view in partial cross-section showing acontainer engaging the chuck assembly according to the first exemplaryembodiment of the present invention in an intermediate position whereinthe container is partially engaged with and partially disengaged fromthe chuck assembly;

[0031]FIG. 6(c) is a side view in partial cross-section showing acontainer and the chuck assembly according to the first exemplaryembodiment of the present invention is in a disengaged position with thechuck just releasing the container into a released state;

[0032]FIG. 7(a) is a diagrammatic side view showing the mechanicalequivalent of the resilient element according to the first exemplaryembodiment of the present invention in a fully engaged state;

[0033]FIG. 7(b) is a diagrammatic side view of a mechanical equivalentof the resilient element of the present invention shown in theintermediate state;

[0034]FIG. 7(c) is a diagrammatic view showing a mechanical equivalentof the resilient element of the present invention in the released state;

[0035]FIG. 8 is a side view in cross-section showing the chuck assemblyof the present invention along with a second exemplary embodiment of theresilient element; and

[0036]FIG. 9 is a side view in cross-section showing the chuck assemblyof the present invention with a third exemplary embodiment of theresilient element according to the present invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0037] The present invention is directed generally to the metal formingmachines that include forming stations operative to receive workpiecesfor performing a machining function thereon. Of particular concern ofthe present invention are improvements to the method and apparatus forejecting a workpiece from such a forming station. Thus, the presentinvention is directed to new and useful embodiments of resilientejectors that may retrofit onto existing chuck assemblies for suchmachines and, furthermore, to the combination of improved chuck elementswith improved resilient ejectors. Thus, the present invention providesboth retrofit capability for existing machines as well as to theimprovements to original (O.E.M.) equipment.

[0038] The present invention is particularly directed to ejectorapparatus and methods for use with lid seaming machines of the typeoperative to seam or join lids or other end caps onto containers such asused in the food and beverage industry. Thus, for purposes of exampleonly and not for limitation as to the overall scope, this invention willbe described hereinafter in conjunction with a lid seaming apparatus fora container, such as a container that has a fiberboard, metal or plasticsidewall. An example of a type of product is a can for frozen juiceconcentrate. It is to be clearly understood from the outset, though,that the exemplary embodiments of the present invention and the methodsemployed could be utilized on other types of machine forming equipment,especially those incorporating ejector rods. Moreover, while thecontainer body is shown to be cylindrical with the end closure (or lid)correspondingly circular, it should be understood that rectangular(including square), oval or other shaped containers and closures as nowknown or later developed are within the scope of this inventionrequiring modifications within the skill of the artisan.

[0039] In order to better understand the present invention; it is firsthelpful to review a standard-type of forming station used in thebeverage can industry. Thus, with reference to FIG. 1, it may be seenthat a standard lid seamer 10 includes an elongated spindle 12 that isfixedly mounted to the machine such as by a housing or turret (notshown). A chuck element 14 is threadably mounted on a distal end ofspindle 12 and includes a working surface 16 that interacts with aforming roller 18 to seam a lid 20 onto a container, such asconcentrated juice container 22. Chuck element 14 and forming roller 18thus define a forming station, and lids 20 are delivered to this formingstation by means of gravity feed 24. Unlidded containers 22 are movedinto position with the forming station, for example, by star wheel 26(shown in phantom). A push pad 28 reciprocates in the direction of arrow“A” and thus provides a positioning mechanism operative to first advanceso as to move container 22 into a engaged position with the formingstation and then to retract whereby the lidded container is ejected fromthe forming station.

[0040] To assist in ejecting the lidded can from the forming station, itis common practice to form a longitudinal passageway 30 through spindle12 to reciprocally mount a knock-out rod 32 therein by means of suitablebearings and bushings. Accordingly, chuck element 14 has a central,axial opening 34 that registers in axially alignment with longitudinalpassageway 30 so that head 36 of knock-out rod 32 may protrude throughopening 34 so as to selectively contact lid 20 thereby to assist inejecting the lidded beverage can from the workstation.

[0041] To supply the knock-out or ejection force, an end 38 of knock-outrod 32 opposite head 36 is connected to a mounting block 40 which inturn is secured to a cam follower 42. Cam follower 42 includes a roller44 received in a camming groove 46 formed in turret portion 48 so that,as the forming station revolves around stationary turret portion 48 inthe direction of arrow “B”, block 40 and thus knock-out rod 32reciprocates in the direction of arrow “C” according to the amplitude ofundulating camming groove 46, as is known in the art.

[0042] As noted in the background of the description, the use of aknock-out rod 32 has disadvantages. The impact of head 36 on the lid 20of container 22 caused by the reciprocating mounting block 40 canscratch or dent the lid or even rupture the seal of the lid thusexposing the contents of container 22 to contamination. Thiscontamination can be in the form of intrusive materials, includingbacteria or other microbes. Additionally, longitudinal passageway 30 isnecessarily supplied with a lubricating medium, such as oil or the like.Any leakage through the bearings, seals or bushings associated withspindle 12 and knock-out rod 32 can contaminate the outer surface of lid20 and, where the edge seal is violated, can possibly contaminate thecontents of container 22. The present invention contemplates eliminationof the entire push rod assembly, including push rod 32, mounting block40 and cam follower 42. This also can possibly permit faster machinespeed by eliminating the inertial mass of the knock-out rod and itsassociated mechanical linkages. The present invention further helpscontrol the lid/end closure during registration with the container body.Accordingly, it should be appreciated that the invention can be employedeither in the manufacture of original equipment or as a retrofitstructure, explained more thoroughly below.

[0043] With reference to FIGS. 2-5, therefore, a first exemplaryembodiment of the present invention is shown in the form of a chuckassembly 110 including a chuck element 120 and a resilient element 150.With reference first to FIGS. 2 and 3, it may be seen that chuck element120 is in the form of a generally cylindrical tool having a surroundingsidewall 122 so that a longitudinally extending passageway 124 is formedtherethrough. Chuck element 120 is constructed identically to thatdescribed in my U.S. Pat. No. 5,533,853, the contents of which areincorporated herein by reference. It should be understood, however, thatdifferently configured chuck assemblies could be used. For example, lidseaming machines with chuck assemblies are used for rectangular(including square) cans and oval cans, such as those used to packagemeat products. Other seaming machines employ chuck assemblies for cansprovided with pull tab openers (such as beverage cans, some pet foodcans, sardine cans, etc.).

[0044] In any event, an inner wall of sidewall 122 is threaded at 126 soas to be threadably received on the threaded end of spindle 12.Returning again to FIGS. 2 and 3, it may be seen that sidewall 122includes a plurality of spanner ports 128 so that a wrench may beengaged with chuck element 120 so as to allow loosening and tighteningof chuck element 120 onto spindle 12.

[0045] A distal end 130 of chuck element 120 includes recess 132surrounded by an upstanding peripheral rim 134. Recess 132 communicateswith a central opening 136 by way of passageway 124 centered aboutlongitudinal central axis “X”. Thus, peripheral rim 134 extends aroundone end of chuck element 120. Where the chuck element 120 is circular,then, the rim 134 extends circumferentially around the end with rim 134having an exterior forming surface 138 which cooperates with formingroller 18 to join or “seam” a lid 20 onto an upper rim of container 22.An annular groove 140 is formed (such as by machining) in recess 132along the periphery thereof proximate to upstanding rim 134. Annulargroove 140 thus has an inner groove wall 141 with an exposed supportsurface 143. Rim 134 and inner groove wall 141 together bound groove140.

[0046] Resilient element 150 is best shown in FIGS. 3-5. As is shown inthese Figures, resilient element 150 includes a compressible, resilient,flexible body 152 having a first portion in the form of central panelsection 153 generally having a first thickness “t₁”. An annular ridgestructure 154 projects away from a first side 156 of central panel 153.Ridge structure 154 is sized and adapted to be matably received inannual groove 140 of chuck element 120 thereby to secure resilientelement 150 in a fastened state in a recess 132 of chuck element 120.Ridge structure 154 has a wall 158 formed at a large acute anglerelative to the plane “P” of central panel 153. This allows ridgestructure 154 to be snap-fitted into engagement with annular groove 140.

[0047] Resilient element 150 includes a second or margin portion definedby a radially outwardly projecting peripheral lip 160 that extendsaround an outer, exposed perilmeter edge of central panel 153. Anannular shoulder 162 extends around the interior 155 of resilientelement 150 adjacent to but radially inwardly of ridge structure 154.Accordingly, resilient member 150 provides an active spring region 164located between annular edge 168 of central portion 153 and shoulder 162as a margin portion of resilient element 150. A spring region 164 isformed of a thickness “t₂” that is greater than “t₁”. Spring region 164provides an ejecting force, when compressed, as described morethoroughly below. An annular ring 170 is located on the exterior surfaceof central portion 153 of resilient element 150 and has an axial bore172 through which a shaft 174 of plug 180 is inserted for mounting.

[0048] With reference to FIG. 4, the construction and assembly ofresilient element 150 may be seen in greater detail. Here, it may beseen that resilient flexible body 152 is sandwiched between plug 180 anda locking washer 190. Flexible body 152 is preferably formed of apolymer material such as neoprene, EPDM or other durable, flexible,compressible, and resilient material. Further, body 152 is constructedto have the configuration described above. Plug 180 has an elongatedaxial shaft 174 provided with a plurality of radially projecting,resilient vanes 182 and an enlarged button or head 184 constructed as anannular disk. Plug 180 is integrally molded as a single piece out ofnylon or other polymer, but is should be understood that it ispreferable to use a hard, stiff, lubricious plastic. In any event, shaft174 of plug 180 is inserted through axial bore 172 and resilient body152 so that head 184 abuts a stanchion in the form of annular ring 170.Plug 180 is held in position by means of a locking washer 190 that ispress-fit onto shaft 174 so as to be engaged and held in position byvanes 182. To this end, washer 190 is provided with a central opening192 to receive shaft 174. Plug 180, along with the flexibility ofcentral portion 153, provides a second active spring region to eject acontainer 22 from chuck assembly 130.

[0049] As is also shown in this FIG. 4, as well as in FIG. 3, centralpanel 153 has a plurality of equiangularly spaced, longitudinallyextending vent passageways 157 that provide vents such that the interiorof chuck element 130 may be vented when resilient element 150 is mountedon the end thereof. The use of vents 157 is desirable, on one hand, toprevent resilient element 150 from forming a suction cup when pressedagainst a lid 20. Should this happen, the suction force would act toresist ejection of the seamed container. Use of vents 157 does increasethe possibility, however, of a small amount of lubricant leakage.Accordingly, depending on the application and risks involved, vents 157may or may not be employed without departing from the scope of thisinvention.

[0050] The action of resilient element 150 on a container 22 can now bemore fully appreciated with reference to FIGS. 6(a)-6(c) and FIGS.7(a)-7(c). Referring first to FIG. 6(a), it may be seen that container22 and lid 20 engage chuck 120 in a fully engaged position. Here, theactive first spring region 164 is compressed against lid 20 whilecentral portion 153 of resilient element 150 is inwardly deflectedbecause of the contact of plug 180 with lid 20. The amount of deflectionis controlled by the thickness of head 184 and the thickness of ring170. FIG. 6(a) corresponds, diagrammatically, to a dual springequivalent of resilient element 150 as is shown in FIG. 7(a). In FIG.7(a), it may be seen that a spring 210 is fully compressed between afirst plate 220 and a second plate 230 spaced at a distance “I₁”.Another spring 250 is fully compressed between plate 230 and a thirdplate 240 a distance “I₂”.

[0051]FIG. 6(b) shows the resilient element of chuck assembly 120 in anintermediate position. Here, the spring region 164 is decompressed thuspartially ejecting, that is, disengaging, lid 20 of container 22 fromchuck assembly 120. However, central region 153 remains substantiallydeflected. This, then, corresponds to the two spring equivalent diagramin FIG. 7(b). In FIG. 7(b), spring 250 remains fully compressed betweenplates 240 and 230 at a distance “I₂”. However, spring 210 isdecompressed so that plates 230 and 240 are spaced from one another adistance “I₃”.

[0052] Finally, with respect to FIG. 6(c), chuck assembly 120 andresilient element 150 are in a fully disengaged state or release state.Here, spring region 164 is fully expanded. Moreover, the spring regionformed by the deflection of central portion 153 is now in itsundeflected, or normal position. This, then, corresponds to themechanical equivalent spring structure shown in FIG. 7(c). In FIG. 7(c),it may be seen that spring 210 is fully open so that plates 220 and 230are spaced the distance “I₃” apart from one another. Spring 250 remainsfully expanded so that plates 230 and 240 are spaced-apart an expandeddistance “I₄”.

[0053] From the foregoing, and in particular reference to FIGS.7(a)-7(c), it may be seen that, as container 22 and unseamed lid 20 areadvanced into engagement with chuck assembly 120, spring 250 firstcompresses at a first spring force “F₁” that is equal to k₁ (I₄-I₂)where “k₁” is the spring constant of spring 250. This compression occursbecause “k₁” is much less than the spring constant of spring 210, thatis, “k₂”. Moreover, the compression of spring 250 corresponds to thedeflecting of central wall portion 153 between the released positionshown in FIG. 6(c) to the intermediate position in FIG. 6(b). Furtheradvancement of container 22 and lid 20 into engagement with chuck 120now results in the compression of spring 210. This corresponds to thecompression of spring region 164 of resilient element 150. This secondforce exerted by this second compression, then, equals k₂ (I₃-I₁).

[0054] With the spring equivalent diagrams of FIGS. 7(a)-7(c) in mindand with further consideration of the structure of resilient element150, it may now be appreciated that resilient element 150 provides adual action on a container 22 and its lid 20 both during engagement aswell as for purposes of ejecting the assembled container from theforming station. When in the fully engaged position, spring region 164exerts the larger spring force on lid 20 over a relatively shortdistance. It may be desirable that this force be approximately twenty tosixty pounds acting over a distance of approximately 0.010 to 0.060inches. This force is provided by the compression of region 164 and actsto initially disengage the assembled container from the engaged positionshown in FIG. 6(a) to the intermediate position shown in FIG. 6(b). Uponthe expansion of region 164, however, a smaller force acts over a longerdistance. Here, the spring force is preferred to be approximately fiveto fifteen pounds acting over a distance of approximately 0.1 to 0.5inches. This longer throw with less force accelerates the seamedcontainer downwardly and helps overcome the frictional engagement ofcontainer 22 with the star-wheel apparatus.

[0055] A first alternative embodiment of the present invention is shownin FIG. 8. In FIG. 8, resilient element 350 is adapted to again mount inchuck assembly 120. Here, however, resilient element 350 is formed asintegral one-piece molding of flexible, resilient, compressible polymermaterial. Accordingly, plug 180 is eliminated. Instead, central portion353 has a head structure in the form of an enlarged external nub 360with rounded surface 361 that is axially disposed so as to bear againstlid 20. Vents, such as vent 357, are provided.

[0056] A third exemplary embodiment of the present is shown in FIG. 9.Here, resilient element 450 is again formed as a single molded piece.However, central portion 453 is thickened to provide a greater ejectionforce and the axial nub 460 has a flattened top surface 462 instead ofbeing rounded. In this embodiment, the vent ports are eliminated.

[0057] From the foregoing, it should be appreciated that the amount ofthe dual acting forces may be altered as should be readily apparent tothose ordinarily skilled in the art. This can be accomplished, forexample by changing the dimensions of shoulder 162 both in thickness andin radial dimension, by changing the thickness of region 164 and bychanging the thickness of central region 153. The distance of throw forthe second spring force can be varied by changing the dimensions of plug180 as well as annular ring 170. The amount of force can be altered bychanging the thickness or dimensions of central region 153. In addition,cuts or other weakening structures such as annular channels could beused to alter the spring constant of the second spring force, all asshould be apparent to the ordinarily skilled artisan.

[0058] Also based on the foregoing, it should be appreciated that thepresent invention contemplates a dual acting method of ejectingworkpieces from forming stations. This method would be that contemplatedby the steps performed by all of the structures heretofore described.Broadly, however, the method would entail providing a first and a secondejection force, of different magnitudes, such that the seamed containeris ejected by applying a first force over a first distance and a secondforce over a second distance. In the exemplary embodiment, the secondforce would be a greater force for a lesser distance while the firstforce would be a lesser force for a longer distance.

[0059] Broadly, the method of the present invention comprises the stepsof securing a resilient element in fixed relation relative to the chuckelement in a manner such that a central portion of the resilient elementwill by contacted by deflected by the workpiece when the workpiece ismoved into the intermediate position thereby to exert a firstrestorative force on the workpiece tending to eject it from the chuckelement. Next, the positioning mechanism is advanced whereby theworkpiece is moved from the intermediate position to the engagedposition simultaneously compressing a margin portion of the resilientelement thereby to exert a second restorative force tending to eject theworkpiece from the chuck element. The workpiece is then held in theengaged position against the restorative forces until the machiningfunction is completed. Thereafter, the positioning mechanism retracts toallow the resilient element to rebound to eject the workpiece. Theresilient element is constructed in such the first and the secondrestorative forces applied thereby are sufficient to eject the workpiecefrom the forming station after the machining function is preformedthereof. For example, the machine may be a lid seamer and the machiningfunction according to this method is seaming a lid or other endenclosure onto a container body.

[0060] Accordingly, the present invention has been described with somedegree of particularity directed to the exemplary embodiment of thepresent invention. It should be appreciated, though, that modificationsor changes may be made to the exemplary embodiments of the presentinvention without departing from the inventive concepts containedherein.

I claim:
 1. In a machine adapted to perform a machining function on aworkpiece wherein said machine has at least one forming stationincluding at least one forming roller and at least one chuck elementhaving a forming surface cooperative with said forming roller to performthe machining function and wherein said machine has a positioningmechanism operative to advance so as to move said workpiece from adisengaged position, through an intermediate position and into anengaged position in said forming station wherein the machining functioncan be performed thereon and to retract whereby wherein said workpiececan be ejected from said forming station, an improvement comprising aresilient element formed of a flexible, compressible first material,said resilient element mounted to said chuck element and positioned sothat when the workpiece is in the intermediate position, a first portionof said resilient element is operative to apply a first force to theworkpiece and when said workpiece is in the engaged position a secondportion of said resilient element different from said first portion isoperative to apply a second force to the workpiece and such that, whensaid positioning mechanism retracts, said first and second portions ofsaid resilient element exert first and second restorative forces,respectively, on said workpiece thereby to eject said workpiece from theforming station.
 2. The improvement according to claim 1 wherein saidfirst portion is defined by a central region of said resilient elementand wherein said second portion is defined by a marginal region of saidresilient element.
 3. The improvement according to claim 2 wherein saidmarginal region is formed as a peripheral lip extending around theperimeter of said resilient element.
 4. The improvement according toclaim 2 wherein said central region has a first thickness and whereinsaid marginal region has a second thickness that is greater than thefirst thickness.
 5. The improvement according to claim 2 wherein saidcentral region is provided with a head structure.
 6. The improvementaccording to claim 5 wherein said head structure is formed as anintegral one-piece construction with said central region.
 7. Theimprovement according to claim 6 wherein said head structure has arounded contact surface oriented to contact said workpiece when saidworkpiece is moved from the disengaged position toward the intermediateposition.
 8. The improvement according to claim 6 wherein said headstructure has a flat contact surface oriented to contact said workpiecewhen said workpiece is moved from the disengaged position toward theintermediate position.
 9. The improvement according to claim 5 whereinsaid head structure is defined by a plug disposed on said centralregion.
 10. The improvement according to claim 9 wherein said plug isformed of a second material different from said first material.
 11. Theimprovement according to claim 10 where said second material islubricious.
 12. The improvement according to claim 9 including astanchion ring disposed on said central region, said plug beingsupported by said stanchion.
 13. The improvement according to claim 1wherein said chuck element has a central axis extending longitudinallytherethrough and a recess formed at one end thereof whereby anupstanding peripheral rim extends peripherally around the one end ofsaid chuck element, said resilient member being disposed in the recess.14. The improvement according to claim 13 wherein a groove is formed insaid recess, said resilient element including a central panel regionhaving a ridge structure projecting away from a first side thereof, saidridge structure operative to be matably received in said groove therebyto secure said resilient element in a fastened state to said chuckassembly.
 15. The improvement according to claim 14 wherein said groovehas a wall formed at a large acute angle relative to a transverse planethat is oriented perpendicularly to the central axis of said chuckassembly and wherein said ridge structure is formed at the large acuteangle whereby said central panel region extends transversely of saidchuck assembly when in the fastened state with said ridge structure andsaid groove being in snap-fitted engagement with one another.
 16. Achuck assembly mountable to a machine adapted to perform a machiningfunction on a workpiece wherein said machine includes a spindle adaptedto releasably mount said chuck assembly and at least one forming rolleroperative to interact with said chuck assembly thereby to form a workstation operative to perform a machining function on said workpiece,said machine including a positioning mechanism operative to advance soas to move said workpiece from a disengaged position, through andintermediate position and into an engaged position in said formingstation wherein the machining function can be performed thereon and toretract whereby said workpiece can be ejected from said forming station,said chuck assembly comprising: (A) a chuck element releasably mountableto said machine, said chuck element having (1) a rim provided with aforming surface cooperative with said forming roller to perform themachining function, and (2) a recess bounded by said rim; and (B) aresilient element mounted to said chuck element and disposed in therecess, said resilient element (1) formed of a flexible compressiblefirst material, and (2) sized and adapted so that (a) when saidworkpiece is in the intermediate position, a first portion of saidresilient element engages said workpiece and is operative to apply afirst force to the workpiece, and (b) when said workpiece is the engagedposition, a second portion of said resilient element different from saidfirst portion is operative to apply a second force to the workpiece, and(c) when said positioning mechanism retracts, said first and secondportions of said resilient element exert first and second forces,respectively, on said workpiece thereby to eject said workpiece from theforming station.
 17. A chuck assembly according to claim 16 wherein saidfirst portion is defined by a central region of said resilient elementand wherein said second portion is defined by a marginal region of saidresilient element.
 18. A chuck assembly according to claim 17 whereinsaid chuck element has an axial passageway extending therethrough, saidcentral region extending transversely across the axial passageway withsaid marginal region being formed as a peripheral lip extending aroundthe perimeter of said resilient element.
 19. A chuck assembly accordingto claim 18 wherein said central region has a first thickness andwherein said marginal region has a second thickness that is greater thanthe first thickness.
 20. A chuck assembly according to claim 19 whereinsaid chuck element has a groove formed in said recess proximately tosaid rim such that the groove is bounded by said rim and an inner groovewall, said resilient element including a ridge structure projecting awayfrom a first side thereof, said ridge structure operative to be matablyreceived in said groove thereby to secure said resilient element in afastened state to said chuck element with said marginal region supportedagainst said inner groove wall.
 21. A chuck assembly according to claim17 wherein said central region has at least one vent port formedtherethrough.
 22. A chuck assembly according to claim 17 wherein saidcentral region is provided with a head structure.
 23. A chuck assemblyaccording to claim 22 wherein said head structure is formed as anintegral one-piece construction with said central region.
 24. A chuckassembly according to claim 22 wherein said head structure is defined bya plug disposed on said central region.
 25. A chuck assembly accordingto claim 24 wherein said central region has a bore formed therethrough,said plug including an enlarged contact head and a shaft extending fromsaid contact head, said shaft mounted through the bore thereby to securesaid plug to said resilient element.
 26. A chuck assembly according toclaim 25 wherein said shaft is provided with at least one vane, andincluding a locking washer operative to engage said vane thereby tomount said plug to said resilient element.
 27. A chuck assemblyaccording to claim 25 wherein said central region has an annularstanchion surrounding the bore, said contact head being supported onsaid stanchion.
 28. A chuck assembly according to claim 24 wherein saidplug is formed of a second material different from said first material.29. A chuck assembly according to claim 28 wherein said second materialis nylon.
 30. A chuck assembly according to claim 16 wherein said rim,said recess and said resilient element are circular in shape.
 31. Achuck assembly mountable to a lid seamer that is adapted to seam a lidonto an upper rim of a container to produce a lidded container, said lidseamer including an elongated spindle having a longitudinal passagewaytherethrough that is adapted to slideably mount an ejector rod and thatis adapted to releasably mount said chuck assembly and including atleast one seaming roller operative to interact with said chuck assemblythereby to define a work station for joining a peripheral edge of saidlid and the upper rim of said container, said lid seamer including apositioning mechanism operative to advance so as to move said lid andsaid container from a disengaged position, through an intermediateposition and into an engaged position in said forming station and toretract whereby said lidded container can be ejected from said formingstation, said chuck assembly comprising: (A) a chuck element releasablymountable to said spindle and having (1) an upstanding rim provided witha forming surface cooperative with said forming roller to perform aseaming function, (2) an axial opening extending therethrough that isaxially aligned with the longitudinal passageway when said chuck elementis disposed on said spindle, and (3) a recess bounded by said rim anddefining a seat; and (B) a resilient element disposed in the recess ofsaid chuck element, said resilient element including (1) a central panelportion formed of a flexible, resilient material, said central panelportion (a) extending across the axial opening and (b) having a headstructure disposed thereon, and (2) a margin portion formed of acompressible material supported against said seat, such that, when saidpositioning mechanism advances said workpiece form the disengagedposition to the intermediate position, said head structure contacts saidlid and said central panel portion flexes with a first force, and suchthat, when said positioning mechanism advances said workpiece from theintermediat position to the engaged position, said margin portioncompresses with a second force, and such that, when said positioningmechanism retracts, said resilient element exerts a restorative force onsaid lidded container thereby to reject said lidded container from theforming station.
 32. A chuck assembly according to claim 31 wherein saidcentral panel poriton has at least one vent port formed therethroughcommunicating with the axial opening in said chuck element.
 33. A chuckassembly according to claim 31 wherein said head structure is formed asan integral one-piece construction with said central panel portion. 34.A chuck assembly according to claim 31 wherein said central panelportion and said margin portion are formed as an integral one-piececonstruction out of a material that is both resiliently flexible andcompressible.
 35. A chuck assembly according to claim 31 wherein saidhead structure is defined by a plug disposed on said central region. 36.A chuck assembly according to claim 35 wherein said central region has abore formed therethrough, said plug including an enlarged contact headand a shaft extending from said contact head, said shaft mounted throughthe bore thereby to secure said plug to said resilient element.
 37. Achuck assembly according to claim 36 wherein said central region has anannular stanchion surrounding the bore, said contact head beingsupported on said stanchion.
 38. A resilient element adapted to mount ona chuck assembly, comprising (A) a central panel portion formed of aflexible, resilient material, said central panel portion; (B) a marginportion extending around said central panel portion and formed of acompressible material; and (C) a head structure disposed on said centralpanel portion.
 39. A resilient element according to claim 38 whereinsaid margin portion is thicker than said central panel portion.
 40. Aresilient element according to claim 38 wherein said head structure isformed as an integral one-piece construction with said central panelportion.
 41. A resilient element according to claim 38 wherein saidcentral panel portion and said margin portion are formed as an integralone-piece construction out of a material that is both resilientlyflexible and compressible.
 42. A resilient element according to claim 38wherein said head structure is defined by a plug disposed on saidcentral region.
 43. A resilient element according to claim 38 whereinsaid central region has an annular stanchion surrounding the bore, saidplug being supported on said stanchion.
 44. A method of ejecting a workpiece from a machine that is adapted to perform a machining functionthereon where said machine includes a chuck element having a seatadapted to receive said workpiece in an engaged position, at least oneforming roller operative to interact with said chuck element thereby todefine a forming station for performing the machining function and apositioning mechanism operative to advance so as to move said workpiecefrom a disengaged position, through an intermediate position and into anengaged position in said forming station and to retract whereby saidworkpiece can be ejected from said forming station, comprising the stepsof: (a) securing a resilient element in fixed relation relative to saidchuck element in a manner such that a central portion of said resilientelement will be contacted by and deflected by said workpiece when saidworkpiece is moved into the intermediate position thereby to exert afirst restorative force tending to eject said workpiece from said chuckelement; (b) advancing said positioning mechanism whereby said workpieceis moved from the intermediate position into the engaged positionsimultaneously compressing a margin poriton of said resilient elementthereby to exert a second restorative force tending to eject saidworkpiece from said chuck element; (c) holding said workpiece in theengaged position against the restorative forces until the machiningfunction is completed; and (d) retracting said positioning mechanismafter the machining function is completed whereby to allow saidresilient element to rebound to eject said workpiece, said resilientelement being constructed such that the first and second restorativeforces applied thereby are sufficient to eject said workpiece from saidforming station after the machining function is performed thereon. 45.The method according to claim 44 wherein said machine is a lid seamerand wherein the machining function is seaming an end closure onto acontainer body.